Separable insulated connectors provide an electric connection between components of an electric power system. More specifically, separable insulated connectors typically connect sources of energy—such as cables carrying electricity generated by a power plant—to energy distribution systems or components thereof, such as switchgears and transformers.
Two common types of separable insulated connectors that are used for this purpose are T-body connectors and elbow connectors. Conventional elbow connectors and T-body connectors are installed into electric power systems and used therein according to similar steps. Thus, the connections described herein with respect to a conventional elbow connector are largely applicable to a conventional T-body connector, and vice-versa.
Separable insulated connectors can connect power cables to an energy distribution component, such as a switchgear or transformer. The power cables are inserted into an opening on one end (usually the bottom end) of the connector. After the cable is inserted into the connector, the connector then can be connected to the energy distribution component. More specifically, elbow connectors often include a bushing with an opening at the top end—and bushings in T-body connectors often include two openings at the top end—that can be connected to an energy distribution component. Alternatively, sometimes another apparatus can be connected to the bushings in the connectors, such as a plug or a probe, which then can be connected to an energy distribution component.
Conventional separable insulated connectors often include an external shell and a semi-conductive insert or faraday cage. The purpose of the insert or faraday cage is to shield all gaps of air within the mating components of the separable insulated connector, as these air gaps can cause corona discharge within the connector. This discharge can occur if there is a voltage drop across the air gaps, and the discharge can corrode the rubber materials often used to make the separable insulated connector. The faraday cage ensures that the various mating components have the same electric potential, and thus prevents corona discharge within the mating components.
The external shell and the semi-conductive insert can be made from a conductive or semi-conductive material. As used throughout this application, a “semi-conductive” material can refer to rubber or any other type of material that carries current, and thus can include conductive materials. The shell and semi-conductive insert are often made of a rubber material, such as ethylene propylene dienemonomer (EPDM) rubber, thermoplastic rubbers (TPRs), silicone rubber, or variety of other suitable materials known to those having ordinary skill in the art and having the benefit of the present disclosure.
The EPDM rubber or other suitable materials can be made using a variety of methods and proportions of components, such that the EPDM rubber can be stiff, soft, or somewhere in between. One particular difficulty that manufacturers of separable insulated connectors face is in determining how flexible a material (such as EPDM rubber) to use in manufacturing the components of a connector. This difficulty arises because a soft shell or insert has certain advantages and disadvantages when compared to a stiff shell or insert.
For example, given that the shell of the connector may be connected to a cable, plug, probe, or energy distribution component, a soft shell may be more flexible in accommodating such cables, plugs, probes, or energy distribution components of a variety of sizes when compared to a stiff shell. The accommodation of an increased variety of cables, plugs, probes, or energy distribution components allows greater flexibility and adaptability for the entire electric power system. The same advantage is true for a soft insert, when compared with a stiff insert.
However, soft shells and inserts may not provide the strength and durability that is desirable for separable insulated connectors. A soft shell or insert may be more likely to warp in case of a power surge or fault current, and may be more likely to accidentally disconnect from the cable and/or energy distribution component. A power surge or fault current can create magnetic forces that repel a soft shell of a separable insulated connector off from a bushing connected thereto. Additionally, a soft shell or insert may not be easily moved, disconnected, or adjusted without tearing or causing other damage to the connector.
Shells and inserts for conventional separable insulated connectors are therefore often made from a material toward the middle of the stiff and soft spectrum, to capitalize on some of the advantages of each. With such an approach, however, the shells and inserts also retain some of the disadvantages of a stiff or soft material, and fail to maximize the advantages of each material.
Thus a need in the art exists for a separable insulated connector in an electric power system that addresses the disadvantages found in the prior art. Specifically, a need in the art exists for a separable insulated connector that includes a shell and/or semi-conductive insert that capitalizes on the advantages of both a soft material and a stiff material, while minimizing the disadvantages associated with each.